Tar sand is composed of a mixture of viscous hydrocarbon compounds, known as bitumen, occupying pore space within rocks such as sandstone, dolomite, and loose sedimentary deposits, with the particles thereof essentially being bitumen in varying amounts adsorbed on sand granules. Deposits of tar sand are found in the ground in many areas of the world, and are removed from the earth through utilization of mining techniques known in the art for subsequent removal and recovery of the bitumen for refining into usable petroleum products.
Traditional commercial methods employed in the removal of bitumen from tar sand include hot water extraction, pyrolysis, and solvent extraction. Hot water extraction involves heating tar sand with steam, hot water, and sodium hydroxide in separation tanks wherein the sand falls to the bottom and the bitumen floats to the top and is then removed for reclamation. Pyrolysis consists of partial combustion of the tar sand to decompose the bitumen molecules into gases and liquids for subsequent recovery and refinement. The solvent extraction method involves mixing tar sand with a solvent in which bitumen is soluble, and then removing the solvent-plus-bitumen from the remaining sand for subsequent recovery of the bitumen.
Use of ultrasonic energy has been disclosed by Sherborne (U.S. Pat. No. 2,670,801), Morrell, et al. (U.S. Pat. No. 2,722,498), Logan (U.S. Pat. No. 2,973,312), Bodine (U.S. Pat. Nos. 3,123,546 and 3,189,536), Branson (U.S. Pat. No. 3,222,221), and Pelopsky, et al. (U.S. Pat. No. 3,497,005) in relation to removal of organic substances from various matter in solvent media. Bodine describes the release from tar sand of petroleum tar (bitumen) in the physical form of a hydrocarbon liquid. However, the prior disclosures do not teach the use of ultrasonic energy in concert with stirring of the solvent as disclosed in the instant application to reduce residence time required for removing bitumen from tar sand and thereby increase efficiency of removal.